Acids vs. Bases: Cleaning Pennies Experiment

Purpose: The purpose of this experiment is
to find out which of four household products can most effectively remove tarnish
off of pennies. Furthermore, the four products have been chosen based on their
acid/base Ph level, which should yield information on which is better for the
cleansing of pennies.

Hypothesis: The hypothesis of this
experiment is that the stronger the acidity of the solution, the better it will
remove the tarnish off pennies. The rational is that tarnish is a sign of
oxidation, whereas, acids release H+ and ion which will combine with the
oxidation on the pennies, and therefore remove the tarnish, whereas, bases
remove H+ from a solution, and henceforth, will have little effect on the
pennies.

Pictured above: Equipment used in this experiment, also pictured is
Scientific AmeriKen's beverage of choice.

Procedure: Into each cup place 5 pennies, in
one cup add lemon juice, the next add baking soda and water, vinegar in the net
cup, and finally ammonia in the last cup. Shake and stir each of the cups to
allow the chemicals to have an effect on the pennies, after 10 or so minutes,
remove the pennies from the cups, dry and compare against other chemicals.

Observations:

Substance added to pennies

Ph level

Observations

Lemon Juice

2.3

All five of the pennies were restored to their coppery color.

Vinegar

3.0

3 of the 5 pennies were nearly restored to coppery color.

Baking Soda and Water

9.0

No effects were observable on the pennies.

Ammonia

11.0

Most pennies are partially cleaned, ammonia
turned blue after process was complete.

Conclusion: The hypothesis was proven true,
and the pennies, were best cleaned by the strongest acid, which in this
experiment was lemon juice. A questionable aspect of this experiment is arisen
with the change of the color of ammonia during the experiment. The blueness of
the ammonia might be a coppery solution, as ammonia may have reacted with the
copper pennies, but it probably just dissolved the blue dye away from the sides
of the dixie cup.